Recording system



March 16, 1965 w. A. Elsl-:LE

RECORDING SYSTEM 3 Sheets-Sheet l Filed Nov. 14, 1962 JONCZOU mlum @QL ,IGME

WILLIAM A. EISELE OZamPm uxowli Uv@ oxoo f 9,09

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A T TORNE Y March 16, 1965 w. A. EISELE RECORDING SYSTEM 5 Sheets-Sheet 2 Filed Nov. 14, 1962 MOOTCZO Cro@ WILLIAM A, EISELE /NVEN TOI? ATTORNEY March 16, 1965 w. A. EISELE 3,173,744

RECORDINGSYSTEM Filed Nov. 14, 1962 s sheets-sheet s x A |S PRESENT f4OX SAMPLE To AREA COMPARATOR OPOXC L TO INCREMENT DETECTOR o -P (PLOT) (TNHIBIT) (OUTSIDE) SMQ 24mg //zSex x AXIS PAST SAMPLE T T T STORAGE NORMAL HIGH SPEED glgglw VOLTAGE DIFFERENCE' A TO FREQUENCY 250x T 5C L CONVERTER 64X 25|x- ADC 4;# f J 242XCOUT vCOUNT PULSE 0 252x SC UP/DOWN OUT 253x ADC V V 254xA SC 255 ADC 256x SC f64x .257xw ADC -.0 EM 242x TO RECORDER WILLIAM A. EISELE /NvE/vro/P A T TOR/VE Y United States Patent tion of Delaware n Filed Nov.. 14, 1962, Ser. No. 237,649 20 Claims. (Cl. 346-34) This invention relates to data plotting systems, and more particularly to a multiplexing system for plotting a plurality of pairs of channels by means of only one line recorder or plotter.

The use of a line recorder to record a function of two variables is well known in the prior art. The most' common case is the recording of a voltage level which varies with respect to time. In such a case, a stylus or pen is moved along a rst axis by a servo system in response to lthe voltage level on a single signal channel, while the record medium is moved along a second axis in response to the passage of time. In a slightly less common case, a stylus is moved along a first' axis by a lirst servo system in response to a rst voltage level on a rst signal channel, and conjunctively along a second axis by a second servo system in response to a second voltage level on a second signal channel.

ythe first mentioned system can be used to record any number of variables on respective signal channels, each of which varies with respect to the same function of time, by the addition of a stylus and a servo system for each additional variable. Each stylus must travel along a path which is oiset from the paths of the other styli to prevent interference among the styli.

ln the second mentioned system the record medium does not move, and it is quite difficult to record more than one function of a pair of variables due to interference among the styli. That is, if the plots cross on the record medium, the styli and associated carriers must also cross and interengage. Systems have been proposed wherein when a crossing of plots occurs, the styli and their servo systems exchange signal channels and plots, thereby avoiding the necessity of crossing over each other. While this is feasible, although quite expensive, for two functions, it is prohibitively expensive for more than two functions and their associated styli and servo systems.

To avoid this plot crossing problem, applicant has eveloped a system wherein a single recorder is multiplexcd with any desired number of pairs of signal channels. Although this technique prevents each pair of channels from being recorded continuously and uninterruptedly, it is very practical when a high sampling rate is utilized. It is exceedingly practical when not all of the functions are continuously varying, or varying greatly from onewsampling interval to the subsequent sampling interval. v

It is therefore an object of this invention to provide a single recorder tor plotting a plurality of functions of two independently varying variables.

Another object is to provide a high speed multiplexing system for a plurality of pairs of channels utilizing a single recorder.

Still another object is to provide a high speed multiplexing system which will record only signicant changes in each of the functions being plotted.

Yet' another' object is to provide a multiplexing system which will record only functions which exist between predetermined limits.

A further object is to provide a multiplexing system which will select only functions which exist between predetermined limits and which will provide an enlarged plot of such functions.

Cice

A feature of this invention is the provision of meansfor sequentially and periodically sampling each pair of a plurality of pairs of signal channels; means forstoring a sample signal from eachrpair of channels; and means for sequentially and periodically coupling a single recorder to both a respective storage means and a pair of channels, therebycausing the recorder to plot the change in the signal from the previous sampling period to the present sampling period, and to store a new sample signal in the storage means.

Another feature of this invention is the provision of means for determining whether the change in the signals on a pair of channels from the previous sampling period to the present sampling period exceeds a predetermined minimum, and if it does not, causing the recorder to omit plotting the channels and to proceed to sample the signals on the next pair of channels.

Yet another feature of this invention is the provision of means for determining whether the signals on a pair of channels are within certain predetermined limits, and if they are not, causing the recorder to omit plotting the channels and to proceed to sample the signals on the next pair of channels.

Further objects and features of the instant invention will become apparent from the following description taken in conjunction with the accompanying drawing in which:

FIGURES lA and 1B, taken in conjunction, provide a schematic electrical circuit diagram of the instant invention; and

FGURE 2 is a schematic electrical circuit diagram of a, modification of a detail of FGURES 1A and 1B.

This invention provides a sampling system for a two coordinate recorder or plotter, whereby a single plotter is able to concurrently plot a plurality of input functions, each function being provided by a pair of input signal channels. A multiplexer sequentially and periodically samples each of the pairs of input channels and stores in storage means a sample signal from each sampled channel. During the subsequent sampling period the new or present sample is compared with the old or stored sample, If there is a difference between the values of the samples which is greater than a predetermined increment the change may be plotted. The present sample is also compared with a maximum and a minimum value and if it falls therebetween, and if it also meets the abovementioned predetermined increment condition, the present sample will be plotted. ln this case 'the plotter is connected to the storage means to start its plot at the stored sample value, then the present sample is connected to the storage means to update the storage means and to drive the plotter to the present sample value. It the present sample is not to be plotted because the value is outsideof the maximum and minimum values, the present sample is nonetheless connected to the storage means to update the 'storage means. If the present sample is not to be plotted because the change is less than the predetermined increment, then the storage means is not' updated. f

Turning now to FIGURES 1A and 1B, reference numbers 10X and MY indicate in conjunction the plotter utilized in this invention. The plotter is shown for conjunctively plotting two variables, shown here in an X and Y Cartesian coordinate system. ther coordinate systems might be used. A stylus 12 is carried conjunctively by an X axis movement 14X and Y axis movement 14Y. Each of these movements is controlled by a similar control channel, of which the X channel will be described in detail hereinafter. Equivalent components in each channel will be identified by similar numerals ending in either X or Y as may be appropriate. The stylus amplifier input conductor 2li-AX. Thus, when the plot relay 159 is de-energized, its contact set lSllXC directly connects the conductor llAX to the conductor ZBX, precluding any input signal to the servo amplifier ZtlX and, therefore, any output signal to the servo motor 18X. When the plot relay 15@ is energized, its contact set litXC connects the output of the cathode follower 62X, via the conductor llidX, to the servo amplifier input conductor ZllAX, while conductor llBX remains connected solely to the servo potentiometer center tap 22Xt. Any diierence in voltage levels on the conductors ZQAX and ZBX will be amplified by the servo amplifier ZX and fed to the servo motor iSX, and will also energize the servo relay lll-SX.

Each area detector relay itidX and ltlllY has a contact set llllXC and liltlYC. The lever contacts ot each of the sets ltlYC and ltlhXC are connected to B+, while the normally open lixed contacts of each of the sets is connected to one end of the coil of a relay 156, the other end ot which is connected to a ground return. Thus when either yof out-of-area relays ltllX and ltltlY is energized the relay ide will be energized.

One end of a low resistance resistor 155)( is connected, at loriX, to the conductor MEX which is connected to the output of the cathode follower' 48X. The other end of the resistor lSzX is connected to a junction leX, to

which is connected one end of a high resistance resistor M4K. The other end of the high resistor 164)( is connected to the lever contact of the contact set lSlXC of relay 154. The normally open fixed contact of set llflXC is connected to the conductor 62X which is connected to the X Axis Past Sample Storage 42X. The lever contact of contact set l56XC of relay Se is connected to the junction ltiX. The normally open xed contact of contact set lStiXC is connected to the conductor 62X, and the normally closed fixed contact is connected to the lever contact of contact set lll-oXC of the inhibit control relay M16. The normally open lixed contact of set lllXC is connected to the conductor 62X. Thus, when only relay 146 is energized, and whenever relay 156)( is energized, the conductor IlllZX will be connected to the conductor 62X through the low resistor 153K. When the slow-to-operate relay ld is energized, the conductor MEX will be connected to the conductor 62X through the low resistor ldllX and the high resistor 1eriX in series. A contact set lltZC of the relay 154i is provided to operate the stylus solenoid lo. One end of the solenoid ,le is connected to B+, the other end is connected to the lever contact of set lSLlZC. The normally open fixed contact is connected to a ground return.

A scale control lati, which may be a grid bias level control, may be connected to each of the radio frequency tuned ampliiiers 2132K and i325( and the servo amplihers ZllX and MY to vary the gain of the several amplifiers of the system in conjunction.

@ne end of a resistor 63X is connected to the X axis high area reference conductor @8X and the other end is connected to a junction ll7llX. One end of a resistor 172K, which has a resistance is equal to MSX, is connected to the X axis low area reference conductor 76X, and the other end is connected to the junction 'i'llX. The input of the cathode follower 60X is connected to the junction llllX, and as previously noted, its output is connected, at junction 58X, to one plate of each of the past sample storage capacitors StiX-ElX. This voltage divider network resistors MSX and H2X biases each of the capacitors to a level which is exactly between the levels on the conductors 72X and 74X, i.e., to the center of the X coordinate of the plotting area.

Theory of operation initially the reference levels for the Area Comparators tie-X and @Y are set. Variable resistances 72X, 74X, 7'2Y and MY are acjusted to set the desired maximum and minimum voltage levels on the X axis high conductor CIK o 63X, the X axis low conductor "76X, the Y axis high conductor @SY and the Y axis low conductor MY, respectively. Only the signals appearing within the area, boundaries or frame provided by these four levels are to be plotted. The scale control ldd may be adjusted to provide the desired scale of the system.

ln the irst sampling period, the stepping switch advance mechanism 46 moves each moving contact of each contact bank to the first tixed contact. The first channel pair 30X and SllY are sampled. Consider the X axis channel: The sampled voltage on the conductor StiX kis unidirectionally passed by the cathode follower llX to the conductor 1G25( which is connected to the junction 84X of the area comparator 65X. It the sampled voltage at the junction 84X is above the level on the condoctor 63X or is below the level on the conductor 76X, current will flow through one of the diodes 76 or 90, causing a rise in the grid bias of one of the triodes 94 and 96, which are normally biased to cut-oli, driving the triode into conduction, and resulting in a voltage differential across the coil of the relay ltltX, thereby energizing the relay. The energized out-of-area relay 166K energizes the relay ld and shorts the conductor ltlZX through low resistor 158)( to the conductor 62X. T he resistance of the resistor 153K is very low and is provided only to protect the relay contacts, rThe full sample voltage is now on the conductor 62X and the capacitor 59X is charged to its level. The Y axis channel operates in a similar manner.

if the sampled voltage brought to the junction 54X is within the levels of the voltages on the conductors 72X and 74X, indicating that the plotting point is within the X coordinates of the plotting area, the relay 109K will not be energized. If, also, the inhibit switch B8 is closed to the ground return, then the inhibit relay 146 will be energized, and the conductor leZX will be shorted to the conductor 62X through the low resistor SSX, the normally closed contacts 156XC, and the energized closed contacts 146XC, thereby charging the capacitor 55X to the sampled voltage level.

It the sampled voltage brought to the junction 48X is within the levels of the voltages on the conductors 72X and 74X, indicating that the plotting point is within the X coordinates of the plotting area, the relay llltlX will not be energized. lf, also, the inhibit switch 133 is open, the inhibit relay M6 will not be energized. The present sample voltage on the input conductor 39X will be passed by the cathode follower fil-3X, the conductor ltlZX and the resistor i285( to the node lZtlX of the bridge or the increment detector The past sample voltage on the capacitor 56X, which during this rst sample period will be the area midpoint voltage from the voltage divider MSX-172K, will be passed by the conductor 62X, the cathode follower 64X, the conductor itleX and the resistor lStX to the node llX of the bridge of the increment detector MMX. The bridge circuit was previously balanced, so that no D C. voltage difference existed between the nodes lll-.8X and 116K. Any voltage dilierence now impressed between the nodes 120K and llltX will eect a DC. unbalance between the nodes ldX and MSX and an input signal, via the transformer IMX, to the tuned radio frequency amplifier SZX, which in turn will provide a DC. output to the coil of the relay llBX.

if the ditierence between the present sample and past sample voltage levels is greater than a predetermined value, the DC. output of the tuned RF amplier 132K will operate the contacts of relay leX. it the difference is less than lthe predetermined value, the contacts of relay 13e will not be operated. lf the difference or increment is low, and the relay 136K is not operated, then B+ is not held on the stepping switch advance mechanism de, which moves the moving contacts of the stepping switch 38 4to the next level of fixed contacts. The plot relay l5@ is not enervized, nor is any connection made 'between the conductors 12X and 62X; thus the voltage level stored on the capacitor StlX is not changed, i.e. the storage capacitor is not updated.

If the difference or increment is high, the contacts of the relay 136X will be operated and B-lwill be held on the stepping switch advance mechanism i6 and on the plot relay Edil. The relay contacts lSlXC are operated, connecting the servo amplifier input conductor ZGAX to the past storage capacitor 56X by way of the conductor ltlX, the cathode follower 64X, and the conductor 62X. Any difference between the past sample voltage on the capacitor EtlX and on the center tap ZZXt of the servo feedback potentiometer 22X will apear as an input signal to the servo amplifier ZtlX, which in turn will power the servo motor 18X to drive the stylus X axis movement l/l-X and the center tap ZXI to the mechanical position representative of the past sample voltage. in the first sampling period, this will be midway between the high and the low reference voltage levels. lt may be noted that biasing the storage capacitors StX-oX to this midpoint voltage level also minimizes the effect of any leakage of charge. The maximum possible charge across the plates of the capacitor is one half the difference between the high and low reference voltage levels. The discharge rate is a percentage of the charge. Thus the leakage is always one half or less than one half what the discharge might have been had the capacitors been biased to one of the reference level voltages.

During the initial examination of the sample voltages, the coil of the relay MSX is not energized and the contact set MSXC is in its normally closed position (also the contact set IlLlSYC of the Y channel). When the coil of the plot relay S is energized, its contact set 150C is operated, energizing the coil of the relay 154. The relay 154, however, is of the slow-to-operate type, and before its latcbing contact set 154C can operate, the coil of the relay MSX is energized, opening its contact set lrf-iXC and de-energizing the coil of the relay 154. When the stylus 12 has been moved to the mechanical position representative of the past voltage sample, the coil of the relay MSX is de-energized and its contact set MSXC returns to its normally closed position, again energizing the coil of the relay 154i. The contact set 154C is slowly operated and the coil of the relay is latched from B+ via the contact set 154C and the contact set 150C to the ground return. The contact set 15a-ZC is also slowly operated to energize the write solenoid lo by connecting it between B+ and the ground return, which engages the stylus l2 with the record medium. The Contact set l52XC is also slowly operated and connects the past sample storage capacitor 56X, via the conductor 62X, the high resistor lddX, the low resistor llSSX, and the conductor ltlZX to the output of the cathode follower 48X, which has the present sample Voltage conductor 30X at its input. The capacitor SX is charged or discharged to the level of the present sample conductor 30X. The charging rate is determined by the time constant of the path described above, which is substantially determined by the resistance of the high resistor IMX. During this charging interval, the input conductor ZAX of the servo amplifier is still connected, as previously described, to the capacitor 56X, and as this capacitor is charged or discharged to the present sample voltage level, the servo amplifier ZtlX, the motor 18X, the feedback potentiometer center tap ZZXI, the stylus X axis movement lliX, and the engaged stylus l2 follow, until the present sample voltage level is reached. The output of the servo amplifier is now zero, and the coil of the relay MSX is deenergized. As the storage capacitor 50X approaches the present voltage level, the voltage difference across nodes lltlX and lltiX falls below the predetermined increment. However, the relay lEeX is of the sloW-to-release type, and by the time its contacts sets have de-operated, the capacitor 58X and the stylus X axis movement lei-X are at the electrical and mechanical present sample voltage level and position. When the relay contact set lldXC de-operates, the

coil of the plot relay l5@ is (le-energized, the contact set 156C deoperates, de-energizing the coil of `the relay l54, whose Contact set liSLtZC is in turn de-operated, de-energizing the stylus engage solenoid ftd, thereby releasing the stylus from the record medium. The contact set lSfXC also de-operates, disconnecting the servo amplifier 26X from the stepping switch. The stepping switch advance mechanism also operates, driving the moving contacts of each fixed contact bank to the next level of fixed contacts. The present sample conductor 32X is now sarnpled in conjunction with the past sample storage capacitor 52X. ln this manner each of the conductors 36X through 36X are sampled sequentially. When the last conductor 36X has been sampled, the stepping switch advance mechanism automatically restores the moving contacts to the iirst level of fixed contacts and the next sampling period begins.

The operation during the second and subsequent sampling periods is identical to that described for the iirst sampling period, except that each storage capacitor now ias in store the sample voltage of the prior sampling period rather than the arbitrary mid-coordinate voltage provided by the voltage divider ll63-l7ZX.

As previously indicated the operations of the Y channel are identical to the described operations of the X channel.

The operation of the multiplexer system may be recapitulated as follows:

If either or both of the X or Y present sample voltages is outside the X or Y coordinate high and low reference voltage levels, respectively, the plotting point is outside of the plotting area and not to be plotted. Either or both of the area comparator relays ltitlX and ltltlY will operate, operating the relay 156, which in turn will connect the X and Y present sample conductors to the X and Y past sample storage capacitors, respectively, via the low resistances lSSX and ISSY, respectively; the stepping switch then moves to the next pair of conductors. The past sample storage is thereby updated, but the point is not plotted.

lf the plotting point is within the plotting area, but the inhibit switch for the conductor pair is closed, the relay 146 will operate to connect the X and Y present sample conductors to the X and Y past sample storage capacitors, respectively, via the low resistances 153K and lSSY, respectively. The stepping switch then moves to the next pair of conductors. The past sample storage is thereby updated, but the point is not plotted.

It the plotting point is within the area, the inhibit switch is open, and neither of the X and Y present samples is more or less than the predetermined increment from its respective past sample, then the inhibit relay M6 will not operate; and neither of the X and Y area relays llltlX and lltlY will operate, thus relay l56 will not operate. Further, neither of the increment relays 136X and 136Y will operate, and the stepping switch advance mechanism will be released to advance the moving contacts to the next level of fixed contacts. Thus the past sample storage will not be updated and the point will not be plotted.

If the plotting point is within the area, the inhibit switch is open, and either or both of the X and Y present samples is more or less than the predetermined increment from its respective past sample, then the inhibit relay 146 will not operate; and neither of the X and Y area relays ltltlX and lltiY will operate. Further, either or both increment relays 136)( and liY will operate, holding the stepping switch advance mechanism 46 and operating the plot relay lill?, which connects the X and Y servo ampliers 29X and ZtlY to the X and Y past sample storage cathode followers 64X and @Y respectively. The error output of each servo amplifier operates its respective servo motor to move the X and Y stylus movements to the past sample position. The error outputs also operate either or both of the relays MSX and lt-Y to maintain the relay 154 de-operated. When the stylus movements are both at the past sample position, the relays MSX and 148Y are both ile-operated, permitting the relay ld to operate, to energize the stylus solenoid i6, and to connect the X and Y present smple conductors to the X and Y past sample storage capacitors, respectively, via the high resistors 164K and lftY, respectively. The past sample capacitors charge or discharge to the respective present sample voltages, and the X and Y servo ampliers and motors follow. When the X and Y stylus movements are at the present sample values, the relays MSX and ftd-SY de-operate, the relay 154 de-operates, de-energizing the stylus solenoid le?. The X and Y increment relays also slowly de-operate, cle-operating the relay l@ to disconnect the servo ampliliers and to release the stepping switch advance mechanism to drive the moving contacts to the next level of xed contacts. Thus a line segment has been drawn on the record medium from the past point to the present point, and the past sample storage has been updated.

lt will be appreciated that various moditications of the embodiment of the invention disclosed in FIGURES 1A and 1B are possible. In the event that the negligible lealtage of the capacitors utilized in the past sample Storage of each channel is unacceptable, a digital storage is provided for each channel, eg. 242K, as shown in part in FIGURE 2. A digital type of storage, specically a plurality of serial pulse counters 256K, 2.52K, 2S4X and d/ are respectively substituted for the storage capacitors X, 52X, 54X and 56X. The output terminals of each counter are connected to the input terminals of a respective digital to analog converter ZSlX, 253K, 255K and ZSTX. The output terminal of each analog to digital converter is connected to a lined contact in a banlf` which is engaged by a moving contact ZLlZXCOUT. Each serial counter has a control input terminal which is connected to a fixed contact in a barili which is engaged by a moving Contact ZItZXCCONT. The polarity or the voltage on this terminal determines whether the counter is to count up or down, Each serial counter also has a pulse input terminal which is connected to a iixed contact in a bank which is engaged by a moving contact ZIl-ZXCIN. Pulses received at this terminal step the counter. A voltage-difference-to-frequency converter 264D( has its input terminals connected to the present sample moving contact @XC via the cathode follower 43X, and to the past sample analog output moving contact ZdZXCONT. This converter ZtllX generates output pulses at a rate which is directly proportional to the voltage applied at its input. A converter of this type is made by Dymec, a division of Hewletblacltard Company, under speciiication 5207-1. The converter pulse output terminal is connected to the counter input moving contact ZI-lZXClN, and the converter control terminal is connected to the counter control moving contact MZXCCONT. The converter is controlled to provide pulses at either a high speed rate or a normal rate. A switch 245K, which is equivalent to the inhibit contact set MSXC, and a switch 2565, which is equivalent to the out-of-area contact set lSeXC, are connected to the convertelto cause it to operate at high speed. A switch 254K, which is equivalent to the plot contact set llSlXC is connected to the converter to cause it to operate at normal speed. rhis converter system is substituted for the contact set and resistor system, lLidXC, l'lSXC, l'tiX, lellX and lidXC of FIGURE lA. The biasing system MSX, lzX, X and SSX of FliGURE 1A is omitted. The digital operation ot the system of FlGURE 2 is analogous to the analog operation of the system of FIG- URE lA. When an inhibit switch, e.g. lh, is closed, the switch ZdX is closed to operate the converter odX at high speed to update the storage, e.g. 256K. When the present sample outside the plotting area the switch 256X it closed to operate the converter 254K at high speed to update the storage, eg. ZhX. When the present sample is to be plotted, the recorder is connected to the output of the respective analog-to-digital converter, e.g. ZSIX, via contact 242XCONT, and the recorder is driven to the past sample position. The switch 254K is closed to operate the voltage-difference-to-frequency converter 264)( at its normal rate. The converter determines the polarity of the difference between the present and past sample and provides in response thereto a count-up or count-down signal t0 the counter, eg. 250K, via the contact MZK-COUNT, and a plurality of pulses, via the Contact 242XCIN until the past sample and the present sample are equal. At this time the recorder has been driven to the present sample position and the past sample storage been updated. l have thus shown and described my invention, but l desire it to be understood that it is not coniined to the particular forms or usages shown and described, the same being merely illustrative, and that my invention may be carried out in other Ways without departing from the spirit of my invention, and, therefore, I claim broadly the right to employ all equivalent instrumentalities corning within the scope of the appended claims, and, by means of which, objects of my invention are attained and new results are accomplished, as it is obvious that the particular embodiments herein shown and described are only some of the many that can be employed to attain these objects and to accomplish these results.

What is claimed is: 1. A recording system for a plurality of signal channels comprising:

signal recording means; a plurality of signal storage means; means operative during a first time period for selectively coupling each of said signal storage means to a respective signal channel, thereby storing in said signal storage means a signal representative of the signal on said respective coupledto channel, and then decoupling said selected storage means from said respective channel; means operative during a second time period for lirstly, selectively and individually, coupling said recording means to each of said storage means, thereby driving said recording means to indicate the signal stored in said selected coupled-to storage means, and secondly also coupling said respective signal channel to said selected storage means, thereby driving said recording means to indicate the signal on said respective signal channel during said second time period and to record the change in signal on said respective signal channel from said first to said second time period, and also thereby concurrently storing in said selected coupled-to storage means a signal representa* tive of the signal on said respective coupled-to channel during said second time period. 2. A. recording system according to claim l further including:

means operative during said second time period to compare the signal stored during said rst time period in said selected storage means with the signal on said respective signal channel to determine Whether these signals differ by an extent greater than a given incremental Value, and on determining said difference not to be present, causing said means for coupling during said second time period to omit said coupling and said recording. 3. A recording system for plotting a plurality of signal channels comprising:

signal recording means; a plurality of signal storage means; means operative during a rst time period for selectively and sequentially coupling and decoupling each of said signal storage means to a respective signal channel, thereby storing in said signal storage means a signal representative of the signal on said respective coupled-to channel; means operative during a second time period for selectively and sequentially, firstly coupling said recording means to each of said storage means, thereby driving said recording means to indicate the signal stored in said selected coupled-to storage means, and secondly also coupling said respective signal channel to said selected storage means, thereby driving said selected storage means to store a signal representative of the signal on said respective coupled-to channel during said second time period and concurrently driving said recording means to indicate the signal on said respective coupled-to channel during said second time period and to record the change in signal on said respective channel from said first to said second time period.

4. A system according to claim 3 further including:

increment means operative during said second period to compare the signal stored during said irst time period in said selected storage means with the signal on said respective signal channel to determine whether these signals differ by an extent greater than a given incremental value, and on determining said diilerence not to be present, causing said means for coupling during said second time period to omit said coupling and said recording.

5. A system according to claim 3 further including:

area means operative during said second period to compare the signal on said respective signal channel with a pair of reference signals and on determining the channel signal to have a first relationship to said reference signals, causing said means for coupling to omit the said coupling of said recording means to said selected storage means and to proceed with said coupling of said respective signal channel to said selected storage means.

6. A system according to claim 5 wherein said area means on determining the channel signal to have a second relationship to saidrreference signals, which is different from said i'irst relationship, causing said means for coupling to proceed with said coupling of said recording means to said selected storage means, and said respective signal channel to said selected storage means.

7. A system according to claim 6 wherein said pair of reference signals are a high and a low value signal and said second relationship is established by the value of the channel signal lying between said high and said low values; and said first relationship is established by the value of the channel signal lying outside the range between said high and said low values.

8. A system according to claim 1 wherein each of said storage means includes an analog type storage device.

9. A system according to claim 1 wherein each of said storage means includes a capacitor.

10. A system according to claim 7 wherein each of said storage means includes a capacitor having two plates,

one of said plates being coupled and decoupled by said means operative during said irst time period to said respective signal channel,

the other of said plates being provided with a signal which is midway between said high and said low reference signal values.

11. A system according to claim l wherein each of said storage means includes a digital type storage.

l2. A recording system for a plurality of pairs of signal channels comprising signal recording means for recording two signals in conjunction;

a plurality of pairs of signal storage means;

means operative during a iirst time period for selectively coupling each one of each of said pairs of said signal storage means to a respective one of each of said pairs of signal channels, thereby storing in said signal storage means a signal representative of the signal on said respective coupled-to channel, and then decoupling said selected storage means from said respective channel;

means operative during a second time period for firstly,

selectively and individually, coupling said recording means to each or" said pairs of said signal storage means, thereby driving said recording means to indicate in conjunction the signals stored in said selected coupled-to pair of storage means, and secondly also coupling each said one of said respective pair of signal channels to each said one of said respective pair of selected storage means, thereby driving said recording means to indicate in conjunction the signals said respective pair of Signal channels during said second time period and to record the changes in the signals on said respective pairs of signal channels from said iirst to said second time period, and also thereby concurrently storing in each of said selected pair of coupled-to storage means a signal representative or the signal on each of said respective pair of coupied-to channels during said second time period.

13. A recording system according to claim l2 further including means operative during said second time period to 14. A recording system for plotting a plurality of pairs of signal channels comprising:

signa?` recording means for recording two signals in conjunction;

a pluralitylof pairs of signal storage means; means operative during a first time period for selectively and sequentially coupling and decoupling each one or" each of said pairs of said signal storage means to a respective signal channel, thereby storing in each of said signal storage means a signal representative of the signal on said respective coupled-to channel;

means operative during a second time period for selectively and sequentially, rstly coupling said recording means to each of said pairs of said signal storage means, thereby driving said recording means to indicate in conjunction the signals stored in said selected coupled-to pair of storage means, and secondly also coupling each said one of said respective pair of signal channels to each one of said respective pair of selected storage means, thereby driving said recording means to indicate in conjunction the signals on said respective pair of signal channels during said second time period and to record the changes in the signals on said respective pair of signal channels from said rst to said second time period, and also thereby concurrently storing in each of said selected pair of coupled-to storage means a signal representative of the signal on each of said respective pair of coupled-to channels during said second time period.

15. A system according to claim 14 further including: increment means operative during said second period 16. A system according to claim 14 further including area means operative during said second period to compare each of the signals on said respective pair of signal channels with a respective pair of reference signals .and on determining either of the channel sigatraves i3 nals to have a lirst relationship to said respective reference signals, causing said means for coupling to omit said coupling of said recording means to said selected pair of storage means and to proceed with 14 and also thereby concurrently storing in said selected coupled-to storage means a signal representative of the signal on said respective coupled-to channel during said second time period.

20. A recording system for a plurality of pairs of signal channels comprising:

a signal recording means for recording two signals in conjunction by moving a single stylus means with respect to two axes;

a plurality of pairs of signal storage means;

means operative during a rst time period for selective- Cil pling to proceed with said coupling of said recording means to said selected pair of storage means, and said respective pair of signal channels to said selected ly coupling each one of each of said pairs of said signal storage means to a respective one oi each oi said pairs of signal channels, thereby storing in said pair of storage means. 15 signal storage means a signal representative ot" the 18. A system according to claim l7 wherein each of signal on said respective coupled-to channel, and said pairs of reference signals are a high and a lov. value then decoupling said selected storage means from signal and said second relationship is established by the said respective channel; value of the channel signal lying between said high and said coupling means operative curing a second, subselow values; and said irst relationship is established by the 2O quent, time period for rstly, selectively and individvalue of the channel signal lying outside the range beually, coupling said recording means to each of said tween said high and said low values. pairs ot said signal storage means, thereby driving 19. A recording system for a plurality of signal chansaid recording means to indicate in conjunction the nels comprising: signals stored in said selected coupled-to pair of storsignal recording means; age means, and secondly also coupling each said one a plurality of signal storage means, each storage means of said respective pair of signal channels to each said being adapted to be varied from one signal storage one of said respective pair of selected storage means, condition, through intermediate storage conditions, thereby driving said recording means to indicate in toasecond storage condition; conjunction the signals on said respective pair of coupling means operative during a first, initial, time signal channels during said second time period and period for selectively coupling each of said signal to record the changes in the signals on said respective storage means to a respective signal channel, therepairs of signal channels from said tirst period through by storing in said signal storage means a signal repto the signal on said respective signal channel at said resentative of the signal on said respective coupledsecond time period, and also thereby concurrently to channel, and then decoupling said selected storage storing in each of said selected pair of coupled-to means from said respective channel; storage means a signal representative of the signal on said coupling means operative during a second, subseeach of said respective pair of coupled-to channels quent, time period for firstly, selectively and individduring said second time period. ually, coupling said recording means to each of said storage means, thereby driving said recording means Refel'elles Cited by the Examiner to indicate the signal stored in said selected coupled- UNITED STATES PATENTS to storage means. and secondli/ also coupling Said 2,579,831 12/51 Kamath 346 33 respective s1gnal channel to said selected storage 2 818 321 12/57 Searles ,546*34 means, thereby driving .said recording means to indi- 21953,,777 9/60 Grid1ey" `l' 346 34 Cate the Slgnal On Sald ISpeCUVe Slgl'lal Channel 45 2 958,766 11/60 Evans 340 149 during said second time period and t0 record the 065,466 11/62 Hickman 345 34 change in signal on said respective signal Channel 3,099,512 7/63 Kohler 346 34 from said tirst period through to the signal on said respective signal channel at said second time period, LEO SMILOW, Primary Examiner. 

1. A RECORDING SYSTEM FOR A PLURALITY OF SIGNAL CHANNELS COMPRISING: SIGNAL RECORDING MEANS; A PLURALITY OF SIGNAL STORAGE MEANS; MEANS OPERATIVE DURING A FIRST TIME PERIOD FOR SELECTIVELY COUPLING EACH OF SAID SIGNAL STORAGE MEANS TO A RESPECTIVE SIGNAL CHANNEL, THEREBY STORING IN SAID SIGNAL STORAGE MEANS A SIGNAL REPRESENTATIVE OF THE SIGNAL ON SAID RESPECTIVE COUPLED-TO CHANNEL, AND THEN DECOUPLING SAID SELECTED STORAGE MEANS FROM SAID RESPECTIVE CHANNEL; MEANS OPERATIVE DURING A SECOND TIME PERIOD FOR FIRSTLY, SELECTIVELY AND INDIVIDUALLY, COUPLING SAID RECORDING MEANS TO EACH OF SAID STORAGE MEANS, THEREBY DRIVING SAID RECORDING MEANS TO INDICATE THE SIGNAL STORED IN SAID SELECTED COUPLED-TO STORAGE MEANS, AND SECONDLY ALSO COUPLING SAID RESPECTIVE SIGNAL CHANNEL TO SAID SELECTED STORAGE MEANS, THEREBY DRIVING SAID RECORDING MEANS TO INDICATE THE SIGNAL ON SAID RESPECTIVE SIGNAL CHANNEL DURING SAID SECOND TIME PERIOD AND TO RECORD THE CHANGE IN SIGNAL ON SAID RESPECTIVE SIGNAL CHANNEL FROM SAID FIRST TO SAID SECOND TIME PERIOD, AND ALSO THEREBY CONCURRENTLY STORING IN SAID SELECTED COUPLED-TO STORAGE MEANS A SIGNAL REPRESENTATIVE OF THE SIGNAL ON SAID RESPECTIVE COUPLED-TO CHANNEL DURING SAID SECOND TIME PERIOD. 